Self-propulsion is the phenomenon by which a system generates its own directed motion or force without relying on external connections for propulsion. It represents a fundamental concept in physics, engineering, and biology describing the autonomous generation of movement through internal energy conversion or interaction with the local environment. As a research field, self-propulsion investigates the diverse physical, chemical, or biological mechanisms that drive such autonomous motion, the principles governing its dynamics across various scales (from microscopic particles to macroscopic vehicles), and methods for its control and optimization. Key characteristics include the generation of force or motion originating from within the system itself, often involving dissipative processes and interaction with the surrounding medium. The significance of self-propulsion is critical for understanding natural biological processes, developing autonomous systems, and advancing technologies in areas such as robotics, space exploration, and targeted drug delivery.